Dragline Boom

ABSTRACT

A boom uses formed plates instead of a round pipes for the chords of the boom. Each formed plate provides a flat surface for attaching lacings so that complex coping cuts required for round pipe chords can be eliminated. The boom also displaces lacing attachment points so that overlapping welds in previous boom assemblies are also eliminated. The open back of the formed plate and non-overlapping lacing attachment points eliminate hidden welds and obscured mounting surfaces that make inspections and repairs of current boom assemblies difficult or impossible.

TECHNICAL FIELD

The present disclosure relates to dragline mining machines and particularly to a configuration of boom chord and lacing for dragline machines used in mining.

BACKGROUND

Dragline machines use a large bucket suspended from a boom to move a payload, such as earth or ore, at a worksite. The boom for the dragline may be more than 400 feet long and has numerous weld joints that need routine inspection and periodically need repairs. The boom may be constructed of chords running the length of the boom and lacings that connect the chords with a series of geometric patterns, such as triangles, that provide support for the bucket and payload, as well as the boom itself.

Tubular booms use round steel pipes for chords and lacings with the chords diameter being larger than the lacing diameter. Some lacings are perpendicular to the chords and some are at an angle. In both cases, the end of the lacing must be formed to match the round contour of the mating surface on the chord using a coping cut on the end of the lacing. Further, because the lacings often terminate in the same spot, the weld joints overlap.

The closed interior of the chord pipe makes it difficult to inspect the back side of the weld joint. Further, overlapping weld joints at a particular attachment point on a chord make it difficult to inspect for damage to a weld or lacing. Overlapping weld joints also make repairs costly and time consuming because multiple lacings are affected each time one lacing is repaired or replaced.

G.B. 523,571A (the '571 patent), titled “Improvements in or relating to construction of Buildings” teaches the use of a formed metal plate in a truss with lacing supports that avoids coping cuts for lacing attachments. The '571 patent uses formed metal across one entire side of the triangle-shaped structure. This adds weight and cost that would be unacceptable if applied to a boom structure.

SUMMARY OF THE DISCLOSURE

In one aspect of the disclosure, a boom for a dragline machine includes a plurality of chords, each chord having a first mounting surface and a second mounting surface, the first and second mounting surfaces being planar and forming a reflex angle and the respective inside surfaces for the first and second mounting surfaces being planar and forming an obtuse angle. Each chord may be arranged so that at least one of the first and second mounting surfaces are facing and generally parallel with one mounting surface of another of the plurality of chords. A plurality of lacings may be used to couple respective facing mounting surfaces of the plurality of chords.

In another aspect of the disclosure, a method of making a boom includes forming a metal plate into a chord having outside surfaces at a reflex angle and inside surfaces at an obtuse angle. The method includes forming additional chords from additional metal plates. The additional chords may have an identical cross section to the chord or may have a different shape from the chord. The chord and the additional chords may be coupled with lacing so that one outside surface of each chord faces a respective outside surface of one other chord.

In yet another aspect of the disclosure, a boom for a dragline machine may include three chords, each chord made from a metal plate formed into three planar surfaces, each chord having at least one obtuse angle between adjacent planar surfaces. The boom may also include a plurality of inter-chord lacings made of pipes, each end of each inter-chord lacing lying in a single plane, wherein each lacing is attached between facing surfaces of two chords.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a dragline machine;

FIG. 2 is a perspective view of a portion of a boom of the dragline machine;

FIG. 3 is a perspective view of a detail of the boom;

FIG. 4A is a perspective view of another detail of the boom;

FIG. 4B is a perspective view of an alternate embodiment of the boom detail of FIG. 4A;

FIG. 5 is an end view of a section of the boom;

FIG. 6 is an end view of an exemplary top chord of the boom;

FIG. 7 is an end view of an exemplary side chord of the boom;

FIG. 8 depicts attachment relationships between chords and lacings of an exemplary boom; and

FIG. 9 is an end view of an alternate embodiment of the boom with four chords;

FIG. 10 is a flowchart of a method of making a boom in accordance with the current disclosure.

DETAILED DESCRIPTION

FIG. 1 is a simplified illustration of a dragline machine 100. The dragline machine 100 has a base 102 with an operator station 104. The dragline machine 100 also has a boom 106 that is used to support a bucket 108. The bucket 108 may be dragged along a work site surface 109 to collect and move material.

FIG. 2 is a perspective view of the boom 106 of the dragline machine 100. The boom 106 may include a first chord 110, a second chord 112, and a third chord 114. In the illustrated embodiment, the first, or top, chord 110 has one shape and the second and third chords 112, 114, are generally mirror images of each other and may be symmetric from a manufacturing perspective. In other embodiments, the boom 106 may have asymmetric chords.

The chords 110, 112, 114 are connected using inter-chord lacings. For example, lacing 116 and lacing 120 are perpendicular inter-chord lacings. Inter-chord lacings 118 and 118 a are oblique inter-chord lacings. Internal lacings 122, 124, 126 are connected in whole or in part to other lacings. In the illustrated embodiment, each internal lacing 122, 124, 126 is coupled at one end to one of the chords 110, 112, 114 and at the other end to another lacing 120.

Supports 128 and 130 are disposed along inside surfaces of the chords 110 and 112, 114 respectively and are formed to match the interior regions of their respective chords 110 and 114, as shown in more detail in FIGS. 6 and 7. The supports 128 and 130 may be disposed either at points opposite where lacings are attached or may be attached anywhere mid-span of the lacing attachments to provide strength and stability to the chords on which they are disposed.

FIG. 3 is a perspective view of a detail of the boom 106. FIG. 3 shows the attachment of chord 114 and perpendicular inter-chord lacings 116 and 120 as well as oblique inter-chord lacing 118 a. Also shown is internal lacing 124 a. Each of the lacing attachments may be positioned such that neither the lacing nor its associated weld joint 132 touches or overlaps another lacing/weld joint. This positioning facilitates inspection of weld joints and lacings. The positioning also facilitates repair or replacement of lacings or their weld joints because no other lacing must be cut or removed during the operation, in contrast to current, overlapping lacing implementations.

FIG. 4A is a perspective view of another detail of the boom 106. Perpendicular inter-chord lacing 120 is shown with internal lacings 122, 124, and 126. In an embodiment, the inter-chord lacing 120 is a pipe, similar to other lacings. In another embodiment, the inter-chord lacing 120 may also be formed from a metal plate such that the lacing is open on one side, similar to the chords 110, 112, and 114. The open side of the lacing allows both sides of the weld joint to be visually inspected and the internal lacings 122, 124 and 126 to have flat, planar end cuts, as discussed in detail below.

FIG. 4B is a perspective view of an alternate embodiment of the boom detail of FIG. 4A. In this embodiment, the inter-chord lacing 120A is made from a rectangular pipe with the internal lacings 122A, 124A, and 126A also being made of rectangular pipes. In an alternate embodiment the inter-chord lacing 120A and the internal lacings 122A, 124A, and 126A may be made from square tubing or tubing of another shape. In yet other embodiments, lacings of various shapes may be wed together. For example, an embodiment may use rectangular inter-chord lacings 120A and round internal lacings 124, 126 so that the internal lacings 124, 126 also benefit from having planar end cuts, avoiding the coped end cuts required by round-on-round connections.

In another embodiment, the inter-chord lacing 120A may be formed from a metal plate and may have a U-shaped profile or an asymmetric profile with two sides perpendicular for mounting internal lacings 122A, 124A, and 126A. For example, the inter-chord lacing 120A may have a profile the same or similar to that of the chord 114 illustrated in FIG. 7.

FIG. 5 is an end view of a cross-section of the boom 106. In the illustrated embodiment, the boom has an isosceles triangle shape, with symmetric lacings 116 and a base lacing 120 longer than either side lacing 116. In another embodiment, the boom 106 may have an equilateral triangular cross-section. In this latter case, each chord 110, 112, 114 would be symmetric, similar in shape to chord 110 shown in FIG. 5.

FIG. 5 also illustrates supports 128 and 130, being formed to contact the inside surface of their respective chords 110 and 114. In an embodiment, the supports 128 and 130 are flat metal plates disposed perpendicular to a length of the chord and are welded to the inside surfaces of the chords.

FIG. 6 is an end view of an exemplary top chord 110 of the boom 106. The chord 110 may be formed from a sheet of metal, such as steel. The chord 110 may include a bottom mounting surface 140 and two side mounting surfaces 142 and 144. The mounting surfaces 140, 142, 144 are planar and may be used to attach lacings, either inter-chord lacings or internal lacings. The mounting surfaces 140, 142, 144 form an open inverted frustum shape where the mounting surfaces 140, 142 and 144 may also be considered outside surfaces. Each mounting or outside surface 140, 142, 144 has a respective inside surface 141, 143, 145. The junction of adjacent mounting surfaces, for example, the junction of adjacent mounting surfaces 140 and 142 form a reflex angle 146. The junction of adjacent inside surfaces 141, 143 form an obtuse angle 148. The support 128 is formed to contact in full or in part, each of the inside surfaces 141, 143, 145. Note that a reflex angle is greater than 180 degrees and less than 360 degrees while an obtuse angle is greater than 90 degrees and less than 180 degrees.

FIG. 7 is an end view of an exemplary side chord 114. The chord 114 has outside, or mounting surfaces 150 and 152. Each mounting surface 150 and 152 has a respective inside surface 151 and 153. The adjacent mounting surfaces 150 and 152 form a reflex angle 154. The inside surfaces 151 and 153 form an obtuse angle 156. The chord 114 may include a third leg 157 with an inside surface 158. The additional leg 157 helps increase the stability and load-bearing capability of the chord 114. The support 130 is formed to contact in full or in part each of the inside surfaces 151, 153, and 158.

For both the top chord 110 and the side chord 114, the supports 128 and 130 are coupled to the inside surfaces of the chords. The supports 128 and 130 help prevent the chords 110 and 114 from deflecting due to lacing forces, that is, those forces occurring during both at rest due to gravity and also by movement of the boom when material is loaded and unloaded. The supports 128 and 130 also limit twist and buckling of the chord 110 and 114.

FIG. 8 depicts attachment relationships between chords 110, 114 and lacings 116, 120, and 164 of an exemplary boom 106. The mounting surface 142 of chord 110 defines a first plane. The mounting surface 150 of the chord 114 defines a second plane. The chords 110 and 114 are arranged so that the first and second plane are generally parallel. Therefore, a perpendicular inter-chord lacing 116 attached to the mounting surfaces 142 and 150 will be perpendicular to both chord mounting surfaces 142 and 150.

Similarly, an inter-chord lacing 120 will be perpendicular to both mounting surfaces 152 and 162 of the side chords 112 and 114. A lacing 164 connecting mounting surfaces 144 and 160 will also be perpendicular to the plane defined by those mounting surfaces 144, 160. The end of each of these lacings lies in a single plane and can be cut with a single cut of, for example, a circular saw, band saw, or cutoff saw to form a planar end cut. The complex coping cuts required for round lacing attachment to round chords of prior boom implementations are avoided. As can be seen in FIGS. 3 and 4, even oblique inter-chord lacings or the chord-side attachment end of an internal lacings will have ends that lie in a single plane, i.e., that can be made with a single cut-off cut.

Further, the open frustum shape of the chords 110, 112, 114 allows visual inspection of both sides of weld joints that attached the lacings to the chords 110, 112, 114. This improves the quality of an inspection because both sides of a chord can be easily viewed so that cracks and imperfections can be identified.

FIG. 9 is an end view of an alternate embodiment of a boom 170 having four chords 172, 174, 176, and 178. The four-chord boom uses individual chords with a similar open frustum shape described above that allows inter-chord lacings 180, 182, 183, and 186 to have planar end cuts and internal chords 188, 190 to have at least the chord-ends with planar end cuts. This four chord embodiment also preserves the open back of the chords of FIGS. 6 and 7 so that compared to prior art round-chord booms inspections are easier and more effective and repairs can be more efficiently effected. The additional feature of offset lacing welds is also maintained in this embodiment.

INDUSTRIAL APPLICABILITY

FIG. 10 is a flowchart 200 of a method of making a boom 106. At a block 202, a metal plate may be formed into a chord 110 with an inverted frustum shape having outside surfaces at a reflex angle and inside surfaces at an obtuse angle. The metal plate may be steel, aluminum, or another composition.

At block 204, additional chords 112, 114 may be formed from additional metal plates; the shape of the additional chords may be the same or different as the chord formed at block 202.

At block 206, lacings may be formed with a planar end profile. That is, lacings made of round pipe may have ends that form a single plane, either perpendicular to a longitudinal axis of the pipe or oblique to the longitudinal axis. For example, the chord-end of any lacing may be cut with a band saw, a cutoff saw, or a circular saw.

At block 208, the chord 110 and the additional chords 112, 114 may be coupled with lacing so that one outside surface 142, 144 of a first chord 110 faces a respective outside surface 150, 160 of one other chord 112, 114. Coupling the chord 110 and the additional chords 112, 114 with lacing may also include attaching each end of a lacing 116 to the outside surfaces 142, 150 of two facing chords 110, 114. Coupling the chord 110 and the additional chords 112, 114 with lacing may also include attaching each end of the lacing so that no lacing, e.g., lacing 116, is in contact with another lacing, e.g., lacing 118 a. The lacings are typically attached with welds, but in the case where other materials or composites may be used for the chords, the chords and lacings may have different attachments, such as rivets, bolts, or epoxies.

At block 210, a support 128, 130 may be disposed between the inside surfaces of the chord. The support 128 130 may be a formed plate that is attached perpendicular to a length of a chord 110, 112, 114 and in contact with the inside surfaces 141, 143, 145 and 151, 153, 158 of respective chords 110, 114. Chord 112 may be a mirror image of chord 114 and has similar inside surfaces that contact similar supports. The supports 128, 130 may be disposed opposite points where a lacing is attached or may be disposed mid-span between lacings.

The use of formed chords rather than tubular pipe chords has the advantage of allowing both sides of a weld joint to be inspected and repaired. The separation of lacing attachment points allows a lacing and its welds to be individually inspected and, if needed, repaired without impacting other lacings. Dragline machine booms 106 are typically inspected every month. Since a boom 106 of a dragline machine 100 may be over 400 feet long and have hundreds, if not thousands, of lacings and welds, any improvement in the inspection and repair processes may have a considerable impact on machine up-time. However, the advantages of the chord and lacing techniques disclosed herein are not limited to dragline machines 100. Any chord-based support structure may benefit from the formed chord and offset lacings discussed in this disclosure, including, but not limited to, portable cranes, overhead cranes, conveyor system supports, antenna towers, etc. 

What is claimed is:
 1. A boom for a dragline machine comprising: a plurality of chords, each chord having a first mounting surface and a second mounting surface, the first and second mounting surfaces being planar and forming a reflex angle and respective inside surfaces for the first and second mounting surfaces being planar and forming an obtuse angle, each chord being arranged so that at least one of the first and second mounting surfaces are facing and generally parallel with one mounting surface of another of the plurality of chords; and a plurality of lacings coupling respective facing mounting surfaces of the plurality of chords.
 2. The boom of claim 1, wherein at least one of the plurality of chords has a third mounting surface.
 3. The boom of claim 1, wherein a weld joint coupling one of the plurality of lacings to the first mounting surface of one of the plurality of chords is non-overlapping with weld joints for other lacings.
 4. The boom of claim 1, further comprising an internal lacing coupled between one of the plurality of chords and one of the plurality of lacings, the internal lacing having at least one end with a planar end cut.
 5. The boom of claim 4, wherein at least one of the plurality of lacings or internal lacings is a rectangular pipe.
 6. The boom of claim 1, wherein the boom further comprises supports disposed between the inside surfaces of the chord and are perpendicular to a length of the chord.
 7. The boom of claim 6, wherein at least one support is disposed opposite each point where a lacing is coupled to one of the first and second mounting surfaces and at least one other support is disposed between points where lacings are coupled to one of the first and second mounting surfaces.
 8. A method of making a boom comprising: forming a metal plate into a chord having outside surfaces at a reflex angle and inside surfaces at an obtuse angle; forming additional chords from additional metal plates; coupling the chord and the additional chords together with lacing so that one outside surface of each chord faces a respective outside surface of one other chord.
 9. The method of claim 8, further comprising forming each lacing with a planar end profile.
 10. The method of claim 8, wherein coupling the chord and the additional chords with lacing comprises attaching each end of a lacing to the outside surfaces of two facing chords.
 11. The method of claim 8, wherein coupling the chord and the additional chords with lacing comprises attaching each end of the lacing so that no lacing is in contact with another lacing.
 12. The method of claim 8, further comprising disposing a support between the inside surfaces of the chord.
 13. The method of claim 12, wherein disposing the support between the inside surfaces of the chord comprises disposing the support opposite a point where a lacing is attached at a corresponding outside surface.
 14. The method of claim 12, wherein disposing the support between the inside surfaces of the chord comprises attaching a formed plate perpendicular to a length of the chord and in full contact with the inside surfaces of the chord.
 15. The method of claim 12, wherein disposing the support between the inside surfaces of the chord comprises disposing the support mid-span between lacing attachment points.
 16. A boom for a dragline machine comprising: three chords, each chord made from a metal plate formed into three planar surfaces, each chord having at least one obtuse angle between adjacent planar surfaces; a plurality of inter-chord lacings made of pipes, each end of each inter-chord lacing lying in a single plane, wherein each lacing is attached between facing surfaces of two chords.
 17. The boom of claim 16, further comprising a plurality of supports fastened between surfaces of the chord.
 18. The boom of claim 17, wherein at least one of the plurality of supports is disposed on the chord opposite each point where a one of the plurality of inter-chord lacings attaches to the chord.
 19. The boom of claim 16, wherein each of the plurality of inter-chord lacings are arranged so that the lacings only contact the two chords and no other lacings.
 20. The boom of claim 16, wherein an outside surface defines a reflex angle of the chord wherein each of the plurality of inter-chord lacings are coupled to the outside surface of the chord. 